Method of synchronizing the change of digits in absolute-value measuring devices and apparatus therefor

ABSTRACT

A method of synchronizing the change of digits in the indicator of absolute-value measuring devices. The method makes use of three possible electrical signals of different amplitude level obtained from scanning at least one track of markings subdividing the track to a certain degree of fineness, and of a control signal obtained from scanning a track of higher fineness. The combined signals control a threshold value discriminator of which the output signal is used for changing the digits. An apparatus for practicing the method comprises a displaceable record carrier having tracks of different degrees of fineness thereon with only one sensing means associated with each track. Each sensing means is connected to a summing circuit stage which, further, is in connection with the sensing means associated with the track of higher fineness. The summing circuit stage is, in turn, connected to the threshold value discriminator.

A United States Patent Heitmann et al.

[451 June 20, 1972 [54] METHOD OF SYNCHRONIZING THE CHANGE OF DIGITS INABSOLUTE- VALUE MEASURING DEVICES AND APPARATUS THEREFOR [72] lnventors:Knut Heitmann, Wetzlar; Eckart Schneider, Berghausen, both of Germany73] Assignee: Ernst Leltz GmbH, Wetzlar, Germany [22] Filed: July 20,I970 [21] Appl. No.: 56,372

Primary Examiner-James W.Lawrence Assistant E.raminerD. C. NelmsAttorney-Krafft & Wells [57] ABSTRACT A method of synchronizing thechange of digits in the indicator of absolute-value measuring devices.The method makes use of three possible electrical signals of differentamplitude level obtained from scanning at least one track of markingssubdividing the track to a certain degree of fineness, and of a controlsignal obtained from scanning a track of higher fineness. The combinedsignals control a threshold value discriminator of which the outputsignal is used for changing the digits. An apparatus for practicing themethod comprises a displaceable record carrier having tracks ofdifferent degrees of fineness thereon with only one sensing meansassociated with each track. Each sensing means is connected to a summingcircuit stage which, further, is in connection with the sensing meansassociated with the track of higher fineness The summing circuit stageis, in turn, connected to the threshold value discriminator.

6 Claims, 6 Drawing Figures PATENTED JUN 2 0 i972 SHEET 10F 2 KNUTHEITMANN ECKART SCHNEIDER HIVE/VTUPZ METHOD OF SYNCI-IRONIZING THECHANGE OF DIGITS IN ABSOLUTE-VALUE MEASURING DEVICES AND APPARATUSTHEREFOR BACKGROUND OF THE INVENTION The present invention relates to amethod of measuring a parameter of an object and indicating the value ofthe measured-parameter in digital presentation and to apparatus forperforming the method.

In digital measuring systems, it is possible for several digits of thenumber to change at the same time when changing from one number to thenext. The same is also true for coded representations of numbers such asare used to an increasing extent in modern measurement engineering. Inthe case of binary coding, for example, when changing from binary 7 tobinary 8, four digits of the symbolic representation change at the sametime. If one scans a record support provided with scale markings anduses a simple scanning slot, then as a rule an absolutely simultaneouschange of the four digits does not take place because the tracks of therecord' support are not aligned with one another with the requisitedegree of accuracy due to normal manufacturing tolerances. One istherefore compelled to use additional aids for obtaining an unambiguouspresentation. I

A well known method of obtaining such presentation from record carriershaving tracks thereon is the socalled V-sensing method. For performingthis method two sensing means are associated with each track, except thetrack which has the highest degree of fineness with which only onesensing means is associated. The latter is connected to a digitalcircuit and when a signal is received by it one of the two receiversassociated with the next track is switched on for sensing. The newlyswitched-on sensing means supplies its output signal to a furtherdigital circuit which, in turn, switches on the sensing means of thenext track, and so on. In this manner the presentation of each track isobtained from the momentary position of the sensing means relative tothe record carrier. By subsequent scanning of the sensingmeansassociated with each individual track the data of the position of therecord carrier is obtained. This prior-art method is rather complicatedwithregard to the required elements.

In another known method one particular track, associated with anadditional sensing means, is allocated to each decade. Thereby thenumber of the required sensing means is considerably reduced, however anadditional track per decade must be provided on the record carrier. Thisrequires additional space on the record carrier and, moreover, alltracks must be precisely aligned to one another, thereby rendering theproduction more difficult.

It is, therefore, an object of the present invention to provide a newmethod of synchronizing the change of digits in absolute-value measuringdevices which overcomes the above described disadvantages.

SUMMARY OF THE INVENTION the sensing of the absence or presence orquantity of one said marking by providing a corresponding electricaloutput signal respectively at either below a first amplitude level orabove a second amplitude level higher than said first level or at anamplitude level intermediate said first and second levels, the sensingmeans associated with the most finely divided track being responsive tothe sensing of the absence or presence of a mark by providing acorresponding electrical control signal respectively at either below thefirst level or at the intermediate level, applying the output signal orsignals and the control signal via a summing circuit stage to adiscriminator circuit having a threshold value such as to provide aresponse signal only in the presence of an output signal in excess ofsaid second level or in the simultaneous presence of a control signaland an output signal of said intermediate level, and applying saidresponse signal to means indicative of the position of the trackassociated with said output signal.

According to the invention, there is further provided an arrangement forcarrying out the method, the arrangement comprising a record carrier,which is displaceable in response to the value of the parameter to bemeasured and which is provided with a set of at least two tracks eachcarrying markings subdividing the tracks to different degrees offineness, sensing means individually associated with each track to scanthe markings thereon, each sensing means associated with any but themost finely divided track being responsive to the sensing of the absenceor presence or proximity of one said marking by providing acorresponding electrical output signal respectively at either below afirst amplitude level or above a second amplitude level higher than saidfirst level or at an amplitude level intermediate said first and secondlevels, the sensing means associated with the most finely divided trackbeing responsive to the sensing of the absence or presence of a mark byproviding a corresponding electrical control signal respectively ateither below the first level or at the intermediate level, meansapplying the output signal or signals and the control signal via asumming circuit stage to a discriminator circuit having a thresholdvalue such as to provide a response signal only in the presence of anoutput signal in excess of said second level or in the simultaneouspresence of a control signal and an output signal of said intermediatelevel, and means applying said response signal to means indicative ofthe position of the track associated with said output signal.

According to one refinement of the invention, for the production of theoutput signals at three different levels, each but the most finelydivided tracks may be provided with markings of intermediate value ateach transition between the presence and the absence of a marking, andeach sensing means associated with any but the most finely divided trackmay be arranged to scan the respectively associated track through aslit.

According to another refinement of the invention, the production of theoutput signals at three different levels,'each sensing means associatedwith any but the most finely divided track is arranged to scan therespectively associated track through a stepped slit.

According to yet another refinement of the invention, for the productionof the output signals at three different levels, each sensing meansassociated with any but the most finely divided track is arranged toscan the respectively associated track through at least two slits spacedapart in the direction of the displacement of the second carrierrelative to the scanning means.

BRIEF DESCRIPTION OF DRAWINGS The invention will be more readilycomprehended from the following description when taken in conjunctionwith the appending drawings, wherein:

FIG. 1 illustrates by electrical waveforms the problem to be dealt within the performance of the invention,

FIG. 2 illustrates by electrical waveforms the principle of the solutionof the problem provided by the present invention,

FIG. 3 illustrates schematically one embodiment of apparatus forperforming the method according to the invention,

FIG. 4 illustrates schematically a further embodiment of such apparatus,and

FIGS. 5a and 5b each illustrate a modification of the apparatusillustrated by FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention proceeds from thefact that a sensing means may respond not only to two but to moredifferent kinds of signals by the production of electric signals ofdifferent levels. If one has a coarsely subdivided and a finelysubdivided track side by side on a record support, then on the recordsupport being displaced in the direction of the tracks and relatively tothe sensing means associated with the tracks, signals are obtained asshown diagrammatically in FIG. ll when slots of different widths areused. Whereas during such a displacement, the signal from the scanningof the finely subdivided track changes as a step function, thetransition of the signal from the scanning of the coarsely subdividedtrack is spread over a longer distance of displacement, so that oneobtains a relatively slowly rising front edge for the output signalpulse of the sensing means. If now one fixes two levels 8,, and S whichare within the dynamic range of the output signal of the sensing means,one can define three signals or signal ranges I, II and III, whichdiffer in their level. The signal III specifies the tolerance range T,in which at any point the stepping of the coarse figure digit must takeplace, namely according to the signal which results from the scanning ofthe finely subdivided track and which changes its level abruptly at thepoint X, of the record support.

Now it is known that the exceeding of a level can be detected the moreaccurately, the steeper the rising flank of the exceeding signal.Moreover, it is required that the threshold value of the discriminatorcircuit should be reached by an output signal III only in combinationwith the control signal obtained from the scanning of the finelysubdivided track. For these reasons, one should aim at a signaloriginating from the scanning of the coarsely subdivided track like thatshown in FIG. 2. In this case, it is desirable for the tolerance range There to be considerably wider than in FIG. ll. Furthermore, the signallevel within this tolerance range is accurately defined and its value ispractically constant. Such a waveform of the output signal III can beobtained in various ways.

FIG. 3 shows one arrangement of suitable apparatus in which the sensingmeans are photo-electric receivers. A photo-electric receiver 11associated with a coarsely subdivided track has allocated to it a gap112 in a shutter 12'. Furthermore, at value change-over of the tracklocated in the range T, a marking 13, of a value intermediate that ofthe presence and of the absence of a mark, determines the tolerancerange T by the space it covers in the transitional range. If the part Mof the track is located behind the gap 12, no light from a lamp 16 canreach the photo-electric receiver 11. Its output signal is thus thesignal I. If the division is located behind the gap in the positionshown, the receiver emits the output signal III. Only when the part ofthe track is located behind the slot 12 is the receiver fully active andsupplies the output signal II. The succession of the signals I, III andII gives the desired course of the level at the output of the receiverII as shown in FIG. 2.

Instead of the straight slot, one may alternatively use a stepped slotand in this case dispense with the intermediate value marking on thetrack.

FIG. 4 shows an embodiment of the apparatus, in which the coarsedivision is carried out without an intermediate value marking. In orderto obtain the desired waveform of the output signal here, two slots 22and 23, which are rigidly coupled together, are associated with thereceiver 11. Their distance from one another is such that, for a desiredtolerance range T, there is only a partial modulation of the receiver11, because both the opaque part 14 and also the transparent part 15take part simultaneously in the signal formation.

The manner in which the distance between the slots can be differentlyarranged relative to the marking division intervals, is illustrated inFIGS. 5a and 5!). FIG. 5a shows one arrangement, in which the distancebetween the two slots 22 and 23 is greater than a division interval C ofthe division. It is C'n+T, in which n is an integer. In the exampleillustrated by FIG. 5b, the

distance between the slots is C'n+T. Instead of the two slots shown, itis also possible to use two groups of slots, the slots within a groupalways being staggered in relation to one another by C or On, and thetwo groups having the above mentioned distances C-n-l-T or Cn-T,respectively.

Although the function of the arrangements has been described in relationto optical apparatus and photoelectric sensing means, the method mayalso be performed to advantage with other types of apparatus, forexample with magnetic recording, and sensing means of appropriate type.

We claim:

l. A method of synchronizing the change of digits in absolute-valuemeasuring devices comprising the steps of;

causing a record carrier provided with a set of at least two tracks eachof which carry marking subdividing the tracks to different degrees offineness to be displaced in response to the value to be measured,

scanning each track other than the most finely divided by an individualassociated light scanning means responsive to the quantity of themarking sensed to generate an electrical output signal of first, secondor third magnitude,

generating an output signal of first magnitude below a predeterminedfirst level in response to the absence of a mark quantity,

generating an output signal of third magnitude above a predeterminedsecond level in response to the presence of a full mark quantity,

generating an output signal of second magnitude intermediate the firstpredetermined level and the second predetermined level in response tothe presence of a half mark quantity,

scanning the most finely divided track by an individual associated lightscanning means responsive to the absence or presence of a mark togenerate an electrical control signal of first or second magnitude,

generating a control signal of first magnitude below a firstpredetermined level in response to the absence of a sensed mark,

generating a control signal of second magnitude inter mediate a firstand second predetermined level in response to the presence of a sensedmark,

conducting the output signal and the control signal via a summingcircuit stage to a discriminator circuit stage having a predeterminedthreshhold value,

generating a response signal in response to the presence of an outputsignal in excess of said second predetermined level or to thesimultaneous presence of an output signal and a control signal of saidintermediate level.

2. Apparatus for synchronizing the change of digits in an absolute valuemeasuring device comprising a record carrier displaceable in response tothe quantity of the value to be measured, at least two informationcarrying tracks positioned on said record carrier, coded markings onsaid tracks subdividing said tracks into different degrees of fineness,said markings being full marks, half marks and no marks, light sensingmeans associated individually with each track to scan the markingthereon, each light sensing means associated with other than the mostfinely divided track being responsive to the type of mark sensed togenerate an electrical output of first, second or third magnituderepresentative of the absence of a mark, presence of a half mark orpresence of a full mark respectively, fine track light sensing meansassociated with the most finely divided track being responsive to theabsence or presence of a corresponding mark on said track to generateone electrical control signal of first or second magnitude respectively,said signal of first magnitude being of a quantity below a firstpredetermined level, said signal of third magnitude being of a quantityabove a second predetermined level, and said signal of second magnitudebeing of a quantity intermediate said first predetermined level and saidsecond predetermined level, means conducting the output signal and thecontrol signal via a summing circuit to a discriminator circuit having apredetermined threshhold value whereby the presence of an output signalin excess of said second level or the simultaneous presence of a controlsignal and an output signal of second magnitude will cause saiddiscriminator circuit to generate a response signal, and meansconducting said response signal to means digitally indicative of theposition of the track associated with said output signal.

3. An apparatus as claimed in claim 2, wherein for the production of theoutput signals at three different levels, each but the most finelydivided tracks are provided with markings of intermediate value at eachtransition between the presence and the absence of a marking, andwherein each sensing means associated with other than the most finelydivided track is arranged to scan the respectively associated trackthrough a slit.

4. Apparatus for synchronizing the change of digits in an absolute-valuemeasuring device comprising a record carrier displaceable in response tothe quantity of the value to be measured, at least two informationcarrying tracks positioned on said record carrier, coded markings onsaid tracks subdividing said tracks into different degrees of fineness,light sensing means associated with each track other than the mostfinely divided track responsive to the presence or absence of one or twomarkings to generate an electrical output signal of the first magnituderepresentative of the absence of any sensed marking, an electricaloutput signal of the second magnitude representative of the presence ofa single marking and an electrical output signal of the third magnituderepresentative of the presence of two markings, light sensing meansassociated with the most finely divided track being responsive to theabsence or presence of a corresponding mark on said track to generate anelectrical control signal of first or second magnitude respectively,said signal of first magnitude being of a quantity below a firstpredetermined level, said signal of third magnitude being of a quantityabove a second predetermined level, and said signal of second magnitudebeing of a quantity intermediate said first predetermined level and saidsecond predetermined level, means conducting the output signal and thecontrol signal via a summing circuit to a discriminator circuit having apredetermined threshhold value whereby the presence of an output signalin excess of said second level or the simultaneous presence of a controlsignal and an output signal of second magnitude will cause saiddiscriminator circuit to generate a response signal, and meansconducting said response signal to means digitally indicative of theposition of the track associated with said output signal.

5. An apparatus as claimed in claim 4, wherein for the production of theoutput signals at three different levels, each sensing means associatedwith other than the most finely divided track is arranged to scan therespectively associated track through a stepped slit.

6. An apparatus as claimed in claim 4, wherein for the production of theoutput signals at three different levels, each sensing means associatedwith other than the most finely divided track is arranged to scan therespectively associated track through at least two slits spaced apart inthe direction of the displacement of the second carrier relative to thescanning means.

1. A method of synchronizing the change of digits in absolutevaluemeasuring devices comprising the steps of; causing a record carrierprovided with a set of at least two tracks each of which carry markingsubdividing the tracks to different degrees of fineness to be displacedin response to the value to be measured, scanning each track other thanthe most finely divided by an individual associated light scanning meansresponsive to the quantity of the marking sensed to generate anelectrical output signal of first, second or third magnitude, generatingan output signal of first magnitude below a predetermined first level inresponse to the absence of a mark quantity, generating an output signalof third magnitude above a predetermined second level in response to thepresence of a full mark quantity, generating an output signal of secondmagnitude intermediate the first predetermined level and the secondpredetermined level in response to the presence of a half mark quantity,scanning the most finely divided track by an individual associated lightscanning means responsive to the absence or presence of a mark togenerate an electrical control signal of first or second magnitude,generating a control signal of first magnitude below a firstpredetermined level in response to the absence of a sensed mark,generating a control signal of second magnitude intermediate a first andsecond predetermined level in response to the presence of a sensed mark,conducting the output signal and the control signal via a summingcircuit stage to a discriminator circuit stage having a predeterminedthreshhold value, generating a response signal in response to thepresence of an output signal in excess of said second predeterminedlevel or to the simultaneous presence of an output signal and a controlsignal of said intermediate level.
 2. Apparatus for synchronizing thechange of digits in an absolute value measuring device comprising arecord carrier displaceable in response to the quantity of the value tobe measured, at least two information carrying tracks positioned on saidrecord carrier, coded markings on said tracks subdividing said tracksinto different degrees of fineness, said markings being full marks, halfmarks and no marks, light sensing means associated individually witheach track to scan the marking thereon, each light sensing meansassociated with other than the most finely divided track beingresponsive to the type of mark sensed to generate an electrical outputof first, second or third magnitude representative of the absence of amark, presence of a half mark or presence of a full mark respectively,fine track light sensing means associated with the most finely dividedtrack being responsive to the absence or presence of a correspondingmark on said track to generate one electrical control signal of first orsecond magnitude respectively, said signal of first magnitude being of aquantity below a first predetermined level, said signal of thirdmagnitude being of a quantity above a second predetermined level, andsaid signal of second magnitude being of a quantity intermediate saidfirst predetermined level and said second predetermined level, meansconducting the output signal and the control signal via a summingcircuit to a discriminator circuit having a predetermined threshholdvalue whereby the presence of an output signal in excess of said secondlevel or the simultaneous presence of a control signal and an outputsignal of second magnitude will cause said discriminator circuit togenerate a response signal, and means conducting said response signal tomeans digitally indicative of the position of the track associated withsaid output signal.
 3. An apparatus as claimed in claim 2, wherein forthe production of the output signals at three different levels, each butthe most finely divided tracks are provided with markings ofintermediate value at each transition between the presence and theabsence of a marking, and wherein each sensing means associated withother than the most finely divided track is arranged to scan therespectively associated track through a slit.
 4. Apparatus forsynchronizing the change of digits in an absolute-value measuring devicecomprising a record carrier displaceable in response to the quantity ofthe value to be measured, at least two information carrying trackspositioned on said record carrier, coded markings on said trackssubdividing said tracks into different degrees of fineness, lightsensing means associated with each track other than the most finelydivided track responsive to the presence or absence of one or twomarkings to generate an electrical output signal of the first magnituderepresentative of the absence of any sensed marking, an electricaloutput signal of the second magnitude representative of the presence ofa single marking and an electrical output signal of the third magnituderepresentative of the presence of two markings, light sensing meansassociated with the most finely divided track being responsive to theabsence or presence of a corresponding mark on said track to generate anelectrical control signal of first or second magnitude respectively,said signal of first magnitude being of a quantity below a firstpredetermined level, said signal of third magnitude being of a quantityabove a second predetermined level, and said signal of second magnitudebeing of a quantity intermediate said first predetermined level and saidsecond predetermined level, means conducting the output signal and thecontrol signal via a summing circuit to a discriminator ciRcuit having apredetermined threshhold value whereby the presence of an output signalin excess of said second level or the simultaneous presence of a controlsignal and an output signal of second magnitude will cause saiddiscriminator circuit to generate a response signal, and meansconducting said response signal to means digitally indicative of theposition of the track associated with said output signal.
 5. Anapparatus as claimed in claim 4, wherein for the production of theoutput signals at three different levels, each sensing means associatedwith other than the most finely divided track is arranged to scan therespectively associated track through a stepped slit.
 6. An apparatus asclaimed in claim 4, wherein for the production of the output signals atthree different levels, each sensing means associated with other thanthe most finely divided track is arranged to scan the respectivelyassociated track through at least two slits spaced apart in thedirection of the displacement of the second carrier relative to thescanning means.